1. Field of the Invention
The present invention relates to a substrate processing method for performing a denaturing process for denaturing a predetermined substance and a process for dissolving and removing the denatured substance, in manufacturing a semiconductor device by use of, e.g., a dual damascene method. The present invention also relates to a computer readable memory medium that stores a control program for executing a method of this kind.
2. Description of the Related Art
In semiconductor devices, a decrease in the interconnection line space due to miniaturization increases the capacitance between interconnection lines, which makes the signal propagation rate lower, thereby resulting in a delay in operation speed. In order to solve this problem, developments are being made in insulative materials with a low specific dielectric constant (Low-k materials), and multi-layer interconnection lines using such insulative materials. On the other hand, copper is attracting attentions as an interconnection line material, because it has a low resistivity and a high electro-migration resistance. Where copper is used for forming interconnection lines in trenches and/or connection holes, a single damascene method and/or a dual damascene method are frequently used.
FIGS. 1A to 1F are explanatory views showing steps of a process for forming a multi-layer cupper interconnection line, using a dual damascene method. An insulating film (Low-k film) 200 made of a Low-k material is disposed on a silicon substrate (not shown) At first, a lower interconnection line 202 made of copper is formed in the insulating film 200 with a barrier metal layer 201 interposed therebetween. Then, a Low-k film 204 used as an inter-level insulating film is formed thereon with an etching stopper film 203 interposed therebetween. Then, an anti-reflective coating (BARC: Bottom Anti-Reflective Coating) 205 and a resist film 206 are formed in this order on the surface of the Low-k film 204. Then, the resist film 206 is subjected to light exposure with a predetermined pattern and is then development, so that a circuit pattern is formed on the resist film 206 (FIG. 1A).
Then, using the resist film 206 as a mask, the Low-k film 204 is etched to form a via-hole 204a (FIG. 1B). Then, the anti-reflective coating 205 and resist film 206 are removed by, e.g., a chemical liquid process and an ashing process. Then, a sacrificial film 207 is formed on the surface of the insulating film 204 including the via-hole 204a (FIG. 1C). At this time, the via-hole 204a is filled with the sacrificial film 207.
Then, a resist film 208 is formed on the surface of the sacrificial film 207. Then, the resist film 208 is subjected to light exposure with a predetermined pattern and is then development, so that a circuit pattern is formed on the resist film 208 (FIG. 1D). Then, using the resist film 208 as a mask, the sacrificial film 207 and Low-k film 204 are etched to form a wider trench 204b on the via-hole 204a (FIG. 1E). Then, the resist film 208 and sacrificial film 207 are removed to complete the via-hole 204a and trench 204b in the insulating film 204 (FIG. 1F). Then, the via-hole 204a and trench 204b are filled with copper as an upper interconnection line.
Incidentally, the sacrificial film 207 is sometimes made of an Si—O based inorganic material, which is difficult to remove by an ashing process used for removing the conventional resist film. There is a case where a chemical liquid is used to dissolve a film of this kind, but the processing rate is very low.
As a method for removing a sacrificial film of this kind, there is proposed a technique in which a process gas containing water vapor and ozone is used to denature the sacrificial film to be soluble in a predetermined chemical liquid, and then the sacrificial film is removed by the chemical liquid (Jpn. Pat. Appln. KOKAI Publication No. 2004-214388).
However, when a process is performed by a process gas containing water vapor and ozone, a Low-k material used as an inter-level insulating film having a pattern may be damaged. The damage in the pattern may become obvious by a subsequent chemical liquid process.
Further, as described above, a process gas containing water vapor and ozone is used to perform a solubilization process, and then a chemical liquid is used to perform a cleaning process. In this case, a Low-k material may be damaged and thereby increase the specific dielectric constant thereof, which deteriorates effects obtained by using the Low-k material as an inter-level insulating film.